In announcing new sanctions on Russia last week, President Barack Obama was at pains to insist that the standoff over Ukraine doesn't mark the beginning of a new Cold War. No doubt he's right -- but commentary on the Ukraine crisis has continued to embrace the ColdWaranalogy anyway. International observers have done so, too. So have some Russian commentators: "Russians Will Suffer in Putin's New Cold War," warns the opposition Moscow Times.

Apparently, lots of people in the U.S. have similar worries. As I've traveled this month to promote "Back Channel," my novel about the Cuban missile crisis, audience members have peppered me with questions about what they see as the dawning of a new Cold War.

I've tried to be reassuring. The Cuban missile crisis was a unique moment in human history. By bowing to pressure from his hard-liners and sneaking intermediate-range nuclear missiles into Cuba, Soviet leader Nikita Khrushchev set off a chain of events that could easily have led to a war that would have annihilated both the U.S. and the Soviet Union, along with many tens of millions elsewhere around the globe. Even given all the troubles around the world, we face nothing like that today.

Nevertheless, there are lessons from the Cold War in general, and the Cuban missile crisis in particular, that could usefully be applied to the foreign-policy challenges the U.S. faces today -- including the standoff in Ukraine. Two points, I have told my audiences, are particularly apt.

First: Keep your adversary guessing. President John Kennedy's ability to conceal his true intentions from Khrushchev was crucial to the successful conclusion of the Cuban missile crisis. The historian Graham Allison has recently summarized the point nicely: "President John F. Kennedy's resolution of the 1962 crisis involved a subtle mix of threat and compromise, candor and ambiguity, coercion and inducement. If Soviet Premier Nikita Khrushchev had not accepted Kennedy's demand that he announce the withdrawal of Soviet missiles from Cuba within 24 hours, would Kennedy have ordered the air strike he threatened? The answer will never be known, but what seems certain is that Khrushchev would not have removed the missiles without the threat of force."

Allison is right: To this day, we don't know for sure whether Kennedy was really willing to push the button. Despite the hours of tapes, the pages of transcripts, and the volumes of memoirs that the crisis has produced, the fact remains that we cannot get into Kennedy's head. He successfully hid his hand.

Russian President Vladimir Putin understands this strategic tool. At the moment, for example, the North Atlantic Treaty Organization and other Western observers are wondering whether the massing of Russian troops on the border with Ukraine signals imminent invasion. The West is exactly where Putin wants it: trying to guess his intentions.

The Obama administration, by contrast, has developed the maddening habit of publicly ruling out options in advance. To take only the most recent instance, the administration has accused Russia of violating the 1987 Intermediate-Range Nuclear Forces Treaty by testing a ground-based cruise missile. But rather than dangling the possibility of tit-for-tat, the administration has already leaked the news that it won't respond by deploying a similar weapon of its own.

I'm not suggesting that the U.S. should violate the treaty. But there is an advantage to be gained in negotiations if Putin is left to wonder what Obama might do.

I also tell my audiences of a second reason the Cuban missile crisis was resolved successfully -- one which would be difficult to replicate today. Trapped between advisers both hawkish and dovish, Kennedy chose a middle ground: the naval quarantine of Cuba, the decision to use the U.S. fleet to ensure that no further Soviet troops or materiel could get through to the island.

Should a similar crisis arise today, it's not obvious that the U.S. could pull off a successful blockade. Projecting power, even in one's own backyard, is no small thing. The blockade that was crucial to resolving the Cuban missile crisis required more than 150 U.S. Navy battle force ships, out of the 900 afloat in 1962. As of this writing, the Navy's entire roster of battle force ships stands at 290.

Actually, the number is smaller than that. The tally of 290 includes hospital ships and small patrol boats -- not counted until this year. In addition, it counts 11 Ticonderoga-class guided missile cruisers that it is keeping "in a reduced operating status."

In short, it would be enormously difficult -- and would cost a much larger fraction of the Navy -- for the U.S. to pull off a quarantine of Cuba today. Even our advanced technology would help only so much. A ship can be in only one place at one time.

Moreover, the strategy works only when the adversary declines to call your bluff. Khrushchev, after a bit of dithering, chose not to challenge the U.S. blockade line. It was on learning that news -- not the Soviet decision to remove the missiles -- that Secretary of State Dean Rusk made his famous remark that the other fella blinked.

Khrushchev's choice not to test Kennedy's resolve over the blockade provided the crucial advantage -- and the crucial time -- Kennedy needed to conclude the crisis. In the absence of a successful quarantine, the U.S. would have been left with two unpalatable choices: live with the missiles in Cuba or go to war to get them out.

Don't get me wrong. Not even Putin would be foolish enough to try to sneak missiles into Cuba today, not least because there's no particular strategic advantage to be gained, but also because Russia couldn't afford the expense. My point is different. Budget cuts must fall upon defense as they must fall everywhere, but difficulties in projecting power carry genuine costs that matter in a crisis.

So although I try to leave my audiences reassured, the reassurance is mixed with caution. We may not be facing a new Cold War, but the U.S. will only weaken its position in the world by failing to heed the lessons of the old one.

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